phpcms怎么判断用户是否登录

<?php         $userid= param::get_cookie(&#39;_userid&#39;); ?>

{if $userid}           。。。这里写已经登录之后的代码。。。 {else} {/if}

<?php   defined(&#39;IN_PHPCMS&#39;) or exit(&#39;No permission resources.&#39;); class MY_index extends index {     private $times_db;     public function __construct() {         parent::__construct();     } 	public function top_mini() { 		$_username = param::get_cookie(&#39;_username&#39;); 		$_userid = param::get_cookie(&#39;_userid&#39;); 		$siteid = isset($_GET[&#39;siteid&#39;]) ? intval($_GET[&#39;siteid&#39;]) : &#39;&#39;; 		$jsoncallback=isset($_GET[&#39;jsoncallback&#39;]) ? $_GET[&#39;jsoncallback&#39;] : &#39;&#39;; 		//定义站点id常量 		if (!defined(&#39;SITEID&#39;)) { 		   define(&#39;SITEID&#39;, $siteid); 		} 		if($_username){ 			$res["success"]=1; 			$res["message"]=&#39;  &#39;.L(&#39;hellow&#39;).&#39;<a href="&#39;.APP_PATH.&#39;member-account_manage_avatar.html" target="_blank">;@@##@@;; '.get_nickname().' 欢迎回家 <a>;'.L('member_center').'</a>; | <a>;发布信息</a>; | <a>;'.L('logout').'</a>;'; 			$res["message"] = pc_base::load_config('system', 'charset') == 'gbk' ? iconv('utf-8', 'utf-8', $res["message"]) : $res["message"]; 			//get_nickname();//, 			 			} 		else{ 			$res["success"]=0; 			} 			 		if($jsoncallback){       		echo $jsoncallback . "({"items":[".json_encode($res)."]})"; 		}else{ 			echo json_encode($res); 		} 		//echo json_encode($res); 	}  } ?&gt;